An object is immersed in a fluid. In order that the object becomes invisible, it should
|
(a) Behave as a perfect reflector |
|
(b) Absorb all light falling on it |
|
(c) Have refractive index one |
|
(d) Have refractive index exactly matching with that of the surrounding fluid |
(d) Have refractive index exactly matching with that of the surrounding fluid
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A photon of wavelength 6630 Å is incident on a totally reflecting surface. The momentum delivered by the photon is equal to
|
(a) 6.63 × 10–27 kg-m/sec |
(b) 2 × 10–27 kg-m/sec |
(c) 10–27 kg-m/sec |
(d) None of these |
For moving ball of cricket, the correct statement about de-Broglie wavelength is
|
(a) It is not applicable for such big particle |
(b) |
|
(c) |
(d) |
In a P-type semiconductor
|
(a) Current is mainly carried by holes |
|
(b) Current is mainly carried by electrons |
|
(c) The material is always positively charged |
|
(d) Doping is done by pentavalent material |
An electron is travelling along the x-direction. It encounters a magnetic field in the y-direction. Its subsequent motion will be
|
(a) Straight line along the x-direction |
(b) A circle in the xz-plane |
|
(c) A circle in the yz-plane |
(d) A circle in the xy-plane |
A diver in a swimming pool wants to signal his distress to a person lying on the edge of the pool by flashing his water proof flash light
|
(a) He must direct the beam vertically upwards |
|
(b) He has to direct the beam horizontally |
|
(c) He has to direct the beam at an angle to the vertical which is slightly less than the critical angle of incidence for total internal reflection |
|
(d) He has to direct the beam at an angle to the vertical which is slightly more than the critical angle of incidence for the total internal reflection |
What is the coordination number of sodium ions in the case of sodium chloride structure
|
(a) 6 |
(b) 8 |
(c) 4 |
(d) 12 |
$\text{zero}$
$\frac{1}{8}\omega\text{Bl}^2$
$\frac{1}{2}\omega\text{Bl}^2$
$\text{B}\omega\text{l}^2$
